1. Field of the Invention
The present invention relates generally to an automatic vacuum cleaner, and, more specifically, to an automatic pile height sensing and vacuum nozzle height adjusting device.
2. Description of the Prior Art
Many devices are known for manually adjusting a vacuum cleaner height to accommodate different types of floor coverings. A vacuum cleaner nozzle lifting device is disclosed in U.S. Pat. No. 4,437,205 in which an adjustable wheel assembly is moved by a sliding lever with a cam follower. The cam follower engages a cam which is rotatable by a foot operated pedal to successive rotational positions and is held in such positions by tooth engaging notches on a ratchet wheel. Pile height sensing and automatic height adjustment are not disclosed.
In U.S. Pat. No. 4,199,839, a wheel height adjusting mechanism includes an adjusting knob connected to an eccentric block that engages an offset portion of a roller lever.
Other cam-type height adjusting mechanisms are known, including: U.S. Pat. No. 3,683,448 that discloses the use of either a sliding or rotationally operated cam; U.S. Pat. No. 2,734,217 which discloses a push button operated cam; U.S. Pat. No. 2,730,751 that discloses a sliding control lever to move a cammed surface; and U.S. Pat. No. 2,730,752 in which an arcuate section moves cooperatively with the vacuum cleaner handle to adjust nozzle height.
A leaf spring controlled height adjustment is disclosed in U.S. Pat. No. 2,515,671; a pedal operated crank pin moving in a lever slot adjusts vacuum cleaner height in U.S. Pat. No. 2,146,602; while threaded height adjusting means are disclosed in U.S. Pat. Nos. 2,259,386; 2,107,016; and 1,428,734.